588 J Neurol Neurosurg Psychiatry 2001;70:588–596 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.70.5.588 on 1 May 2001. Downloaded from Dementia as a complication of schizophrenia P J de Vries, W G Honer, P M Kemp, P J McKenna Abstract become clear that it is an oversimplification. Objectives—Cognitive impairment is Thus schizophrenic patients have been found to known to occur in schizophrenia, and may have a lower average IQ than the normal popu- be marked in institutionalised patients. lation,4 and to show wide ranging neuropsycho- The aim of this study was to determine logical test impairments, prominent among whether it ever warrants an additional which are deficits in memory and executive diagnosis of dementia. function.56 These deficits have been found in Methods—A population of chronic schizo- drug free78and never treated patients,9 and they phrenic patients who were aged 65 or are not easily attributable to poor motivation, younger and showed no organic risk attention, and cooperation.10–13 factors for dementia were screened for It is also well established that institutional- presence of disorientation. Any showing ised schizophrenic patients, who have the most this underwent neuropsychological test- severe and chronic forms of illness, sometimes ing, physical investigations, and struc- show more marked cognitive deficits which can tural and functional neuroimaging. be detected on the simple “bedside” tests of Information about day to day cognitive general knowledge, recall, copying, etc used to function was also obtained from carers. screen elderly patients for dementia.14–16 Up to Results—Eight patients aged 28 to 64 were 25% of such patients also show age disorienta- identified who showed disorientation; in tion, typically underestimating their age by a all cases this was accompanied by general margin of 5 years or more.17 This phenomenon intellectual impairment and objective evi- has been shown not to be a function of dence of a dementia syndrome. The pre-existing learning disability, prior physical patients’ schizophrenic symptoms were treatments, or institutionalisation, and it forms unexceptional and did not seem suYcient part of a wider pattern of cognitive impair- to account for their cognitive impairment. ment.18 19 Both global intellectual impairment Neuropsychological testing disclosed rela- and age disorientation increase in prevalence tive sparing of visual and visuospatial with advancing age in the population chroni- function and language syntax, but perva- cally in hospital and become commonplace sive deficits in memory and executive over the age of 65.16 20 function. Brain CT demonstrated only In 1976 Marsden21 argued for the logical minor abnormalities but most of the extension of these findings, writing: “I have patients showed frontal or temporal hy- encountered a number of chronic schizo- poperfusion on SPECT. phrenic patients in whom full investigation has http://jnnp.bmj.com/ Conclusions—Dementia in schizophrenia revealed evidence of cognitive impairment and seems to be a real entity with a neuro- cerebral atrophy on air encephalography, psychological signature similar to that of Developmental whereas all other investigations for known Psychiatry Section, frontotemporal dementia. Functional but causes of dementia have been negative.” Department of not structural imaging abnormalities may Nevertheless, despite this and occasional simi- Psychiatry, University also be characteristic. lar statements,22 23 dementia is not normally of Cambridge, UK (J Neurol Neurosurg Psychiatry 2001;70:588–596) considered to supervene in schizophrenia and PJdeVries on September 27, 2021 by guest. Protected copyright. Keywords: schizophrenia; dementia; cognition is not clearly recognised as a complication of University of British the disorder. Such a view also runs counter to Columbia, Vancouver, the prevailing beliefs that schizophrenic cogni- Canada As a “functional” psychosis, schizophrenia has, tive impairment is present premorbidly,24 25 is W G Honer from the beginning of the century, been neurodevelopmental in origin,26 and represents a “static encephalopathy”.27 Finally, little is Department of distinguished from the “organic” psychoses of Nuclear Medicine, dementia and delirium by the absence of any known about the pattern of neuropsychological Southampton General compromise of intellectual function.12 For impairment in severely cognitively impaired Hospital, UK example, in one of the original descriptions of schizophrenic patients and its correlates, if any, P M Kemp the disorder, Kraepelin3 stated that patients in structural and functional imaging. “remain surprisingly clear despite the most vio- Fulbourn Hospital, Cambridge CB1 5EF, lent excitement” and “often know accurately to UK a day how how long they have been in the insti- P J McKenna tution”. This distinction has stood the test of Methods time to the extent that acutely psychotic schizo- Patients with a clinical diagnosis of schizophre- Correspondence to: phrenic patients do not typically show disorien- nia in a large rehabilitation service catering Dr P J McKenna [email protected] tation, memory impairment, or other evidence mainly for chronic psychotic illness were infor- of cognitive failure, and were they to do so mally questioned about orientation in time, Received 3 May 2000 and in investigations would normally be undertaken to place, or person. Any showing evidence of final form 22 November 2000 exclude underlying neurological disease. disorientation were administered a more de- Accepted 8 December 2000 Nevertheless, over the past 20 years it has tailed orientation questionnaire previously www.jnnp.com Dementia as a complication of schizophrenia 589 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.70.5.588 on 1 May 2001. Downloaded from used in a study of institutionalised schizo- Patients over 40 also had ECG. Further inves- phrenic patients.18 This covers general orienta- tigations included autoimmune screen and tion, age orientation, elementary general white cell enzyme assay for metachromatic leu- knowledge, and knowledge about daily (for kodystrophy. Brain imaging included CT in all example, ward) routine. Only patients up to the cases, and MRI where indicated on the basis of age of 65 were included, to avoid the questionable CT findings. Tc 99m HMPAO prevalence of dementia due to organic disease single photon emission computed tomography above this age. Patients were excluded if they (SPECT) was carried out on seven patients had a history of head injury, neurological (one patient refused consent for this proce- disease, or any disease known to aVect brain dure). function, drug or alcohol misuse, or learning DSM-IV criteria for dementia additionally disability. History of known ischaemic heart require that the disturbance in cognitive disease, peripheral vascular disease, or hyper- function cannot be better accounted for by tension were further exclusion criteria. Finally, another disorder such as schizophrenia. This any patients who gave absurd or delusional requirement may partly be in recognition of the responses—for example, stating their age to be fact that cognitive impairment is now accepted 200—were excluded from consideration. in schizophrenia, but it also reflects a long- Patients who made five or more errors on the standing belief that such impairment may orientation questionnaire were studied further sometimes be more apparent than real because to establish whether they met diagnostic crite- of the distracting eVects of symptoms, poor ria for dementia. According to ICD 10 and cooperation, or lack of motivation on perform- DSM-IV, this requires evidence of memory ance. To examine this issue, the patients’ symptoms were rated using the positive and impairment as well as multiple additional cog- 41 nitive impairments (for example, aphasia, negative syndrome scale (PANSS), a 30 item apraxia, agnosia, poor executive function) rating scale designed to assess the full range of psychopathology in schizophrenia; the scale which impair social or occupational function- also contains an item rating disorientation. ing. There must also be evidence for a decline in cognition. Other CNS conditions have to be Results excluded. Eleven patients were identified who failed five Current intellectual level was assessed using or more items on the orientation questionnaire the Wechsler adult intelligence scale (WAIS) to but of these, only eight were cooperative measure IQ, plus the mini mental state enough to permit further investigation. Ages 28 examination (MMSE), a clinically oriented ranged from 27 to 64. All patients met cognitive screening test where a score of 23/24 DSM-IV criteria for schizophrenia, based on out of 30 has become widely used as a cut oV detailed clinical assessment and review of case 29 for dementia. To assess premorbid IQ, notes. All but one patient (see below) had educational achievement was determined, and unexceptional presentations of severe, chronic the national adult reading test (NART)30 was illness. The duration of illness was generally administered. This gives an estimate of best long, ranging from 9 to 30 years. Four of the level of IQ functioning based on ability to pro- patients were chronically in hospital, with the nounce irregular English words, and is rela- remainder being cared for at home by relatives http://jnnp.bmj.com/ tively resistant to the eVects of adult onset (one), living in sheltered accommodation dementing illness. A diVerence in WAIS IQ (two), or being treated on